The technique of hydraulic fracturing (commonly referred to as “fracing” or “fracking”) is used to increase or restore the rate at which fluids, such as oil, gas or water, can be produced from a reservoir or formation, including unconventional reservoirs such as shale rock or coal beds. Fracing is a process that results in the creation of fractures in rocks. The most important industrial use is in stimulating oil and gas wells where the fracturing is done from a wellbore drilled into reservoir rock formations to increase the rate and ultimate recovery of oil and natural gas.
Hydraulic fractures may be created or extended by internal fluid pressure which opens the fracture and causes it to extend through the rock. Fluid-driven fractures are formed at depth in a borehole and can extend into targeted formations. The fracture height or width is typically maintained after the injection by introducing an additive or a proppant along with the injected fluid into the formation. The fracturing fluid has two major functions, to open and extend the fracture; and to transport the proppant along the length or height of the fracture.
Current fracing systems and methods, however, can be expensive and inefficient.
In many cases, it is desired to target the fracturing process at a specific location in a formation. Prior attempts to address this issue include the devices and methods disclosed in Canadian Patent Application 2,755,848 and Canadian Patent 2,692,377, both of which are hereby incorporated by reference in their entirety.
Both of these documents disclose a burst opening for fracing fluid to exit a completion/service string and access a formation. It is known that burst disks can work in a cemented environment, however, both of these tools are problematic to use in practice. When the fluid pressure is used to burst open these tools, only one out of multiple openings will burst. Pressure is lost at that point and the flow area is severely limited.
Attempts to address the issue of using hydraulic pressure to actuate various downhole components include those disclosed in Canadian Patent 2,637,519, Canadian Patent Application CA 2,719,561, and Canadian Patent Application 2,776,560, all of which are hereby incorporated by reference in their entirety. These methods and apparatuses, however, have their shortcomings. A problem with the exposed vent holes of these devices is that they can be prone to being plugged, restricted, or blocked by debris, especially during cementing operations.
Safer, more reliable, and cost-effective fracing methods and systems are quickly becoming sought after technology by oil and natural gas companies. It is, therefore, desirable to provide an apparatus and method for hydraulic fracturing that can overcome the shortcomings of the prior art and provide a greater degree of reliability.